What is an intranet and what security issues surround its use by a corporation?

What will be an ideal response?

Answer: Suggested answer:
An intranet is a self-contained, in-house network or Internet that is used by a company for its own internal communications. Employees within an organization may use an intranet in exactly the same fashion as the Internet; however, the intranet may be partially or completely unavailable to those outside of the organization.

The main security problem with intranets is that such a network can potentially expose the organization's sensitive information to everyone on the Internet. To help avert such a problem, companies use combinations of hardware and software to limit access from outsiders. A firewall is a software program that filters each packet of incoming information to ensure that it has originated from an authorized source. One typical approach is to use IP filtering, which blocks out incoming packets which do not originate from preauthorized IP addresses. Such preauthorized addresses are maintained in an access control list. Unfortunately, such firewall protection can be defeated if an outsider can "spoof" an IP address (by sending incoming message requests that falsely appear to come from an authorized IP address). Firewalls are still useful, but should be considered only the first-line of defense.

Another type of security device used with an intranet is a proxy server. Such servers are used "on the inside" of a company's firewall to filter all outgoing requests for information. If a request is valid (as determined by settings found in an access control list), the request passes through the proxy server; otherwise it is blocked. Proxy servers can also be used "in reverse" to filter all incoming requests, thus preventing unauthorized access to specific locations within the organization. Proxy servers which operate this way provide another type of firewall protection from outside intruders.